Razor blade coating

ABSTRACT

A razor blade substrate having a substrate that includes a blade edge portion having a profiled geometry which is covered by a strengthening coating deposited on the razor blade substrate at least at the blade edge portion. The strengthening coating covering the blade edge tip, having a profiled geometry and having a tapering geometry with two coating sides converge toward a blade edge tip. The strengthening coating includes a strengthening layer made of a titanium- and boron-containing material.

This application is a continuation application of U.S. application Ser.No. 16/565,664, filed Sep. 10, 2019, which is a continuation ofapplication Ser. No. 15/500,698, filed Jan. 31, 2017, which is anational stage application of International Application No.PCT/EP2015/067477, filed Jul. 30, 2015, which claims priority toPCT/EP2014/066511 filed on Jul. 31, 2014, where the entire contents ofboth applications are incorporated herein by reference.

FIELD OF INVENTION

The embodiments of the present invention relate to a razor blade.

BACKGROUND OF INVENTION

In particular, the present invention relates to a razor blade having arazor blade edge.

From the prior art, razor blades have been provided. Suitably placed ina razor cartridge, they offer the ultimate function of cutting the hair.

In the past, razor blades have been provided with a substrate and astrengthening coating covering the substrate at the blade edge. Thestrengthening coating is generally a metal- and/or carbon-containingmaterial, and provides enhanced strength to the razor blade edge, whichin turn enhances its life expectancy.

Sometimes, the strengthening coating is further coated by a lubricatingcoating such as a PTFE coating.

Providing a better coating on a razor blade edge is a challenge. Firstof all, because the razor blade substrate edge has a very peculiargeometry, depositing a coating on it which would operate as a suitablecoating by enhancing the cutting properties and strengthening the razorblade edge is very difficult.

Secondly, since razor blades are a mass consumption goods, the coatingwould have to be applied on a very uniform way from product to product,and at a high throughput (millions of parts per day), which requires acoating compatible with a very reliable process.

Thirdly, even if it were possible to deposit a new coating on a razorblade, measuring the improvement with respect to prior art products isalso very difficult. This is because the perceived quality of shaving bytest panels can be very subjective.

Hence, development of a new razor blade coating takes years of R&D work.

Nonetheless, one is still looking to improve razor blades by providing abetter razor blade coating.

WO 2006/027,016 describes a razor blade coating including chromium andcarbon.

Other prior art documents give endless lists of materials said to besuitable for razor blade coatings. An example of such a document is EP 1287 953. In view of the provided long list of materials, it is likelythat not all of them have been actually tried as razor blade coatingcomponents, and it is also likely that some of them would be unsuitableas razor blade coating components.

One aim, when developing a new razor blade coating, is to increase thehardness of the coating material. There are many materials harder than amixture of chromium and carbon. One possible candidate when looking fora harder material than a mixture of chromium and carbon is titaniumdiboride.

It should be mentioned that there are other coated cutting tools thanrazor blades. These cutting tools have their own issues and structuresdesigned to face these issues. For example, WO 2007/136,777 aims atobtaining a stable cutting edge consisting of a multilayer coating withdifferent architectures on both sides of the blade of a rotary tool.Regarding the coating itself, it includes a specific top wear-resistantlow friction anti-galling segment overlaying a bottom multilayerbondcoating cermet segment which accommodates the internal stresses inthe top segment and secures the highest toughness of the entire coatingsystem. This is a specific coating in view of specific cuttingapplications, where “razor blades” are mentioned as a surgical or dentalinstrument.

Turning back to shaver razor blades, unexpectedly, duringexperimentation in view of depositing a titanium- and boron-containingcoating on a razor blade edge, the inventors have encountered a coatinghaving excellent properties for a razor blade coating.

SUMMARY OF THE INVENTION

The embodiments of the invention relate to a razor blade including ablade edge portion, the razor blade including:

-   -   a razor blade substrate having a substrate edge portion in the        blade edge portion of the razor blade, the substrate edge        portion having a profiled geometry and having a tapering        geometry with two substrate sides converging toward a substrate        tip,    -   a strengthening coating deposited on the razor blade substrate        at least at the blade edge portion, the strengthening coating        covering the substrate tip, the strengthening coating having a        profiled geometry and having a tapering geometry with two        coating sides converging toward a coating tip,

Wherein the strengthening coating includes a strengtheningnanocrystalline layer made of a mixture of titanium and boron includingat least one of titanium-rich areas and boron-rich areas, where “rich”is used by reference to a stoichiometric TiB₂ composition.

The above razor blade has a significantly enhanced hardness, andmanufacturability enabling it to meet the other requirements for a razorblade coating: reliably uniform features at high industrial manufacturethroughput (at reasonable cost).

A “titanium-rich” area refers to an area where the proportion oftitanium is higher than in titanium diboride.

A “boron-rich” area refers to an area where the proportion of boron ishigher than in titanium diboride.

In some embodiments, one might also use one or more of the followingfeatures:

-   -   the average proportion of boron and titanium atoms in the        strengthening layer is between 1.3:1 and 2.3:1;    -   a razor blade, wherein the average proportion of boron and        titanium atoms in the strengthening layer is between 2.01:1 and        2.3:1;    -   the average proportion of boron and titanium atoms in the        strengthening layer is between 1.3:1 and 1.99:1;    -   the nanocrystalline layer includes titanium diboride areas;    -   a razor blade, wherein the areas of titanium diboride are        non-columnar;

a razor blade wherein the strengthening nanocrystalline layer includesnanocrystalline arrangements, wherein the atoms of the nanocrystals arearranged in a hexagonal lattice configuration;

-   -   a razor blade wherein the strengthening layer includes        featureless crystallites having a characteristic dimension        between 2 and 15 nanometres (nm);    -   a razor blade, wherein the strengthening layer is deposited        under conditions which, when applied to deposition on a flat        witness sample, provide a coating with a density which is above        3.9 grams per cubic centimetre (g/cm³);    -   a razor blade, wherein a combined thickness of the blade        substrate and strengthening coating, measured between the two        coating sides orthogonal to a line bisecting the blade edge        portion, at a distance of 5 micrometers from the coating tip, is        between 1.8 and 2.5 micrometers, and preferably between 1.9 and        2.4 micrometers;    -   a razor blade, wherein a combined thickness of the blade        substrate and strengthening coating, measured between the two        coating sides orthogonal to a line bisecting the blade edge        portion, at a distance of 20 micrometers from the coating tip,        is between 5.1 and 7.3 micrometers, and preferably between 5.4        and 7.1 micrometers;    -   a razor blade, wherein the razor blade substrate is made of        stainless steel;    -   a razor blade, wherein the strengthening coating includes an        interlayer between the razor blade substrate and the        strengthening layer;    -   a razor blade, wherein the interlayer includes titanium;    -   a razor blade, wherein the interlayer is made of Titanium;    -   a razor blade, wherein the strengthening coating includes a        metal-containing overcoat layer over the strengthening layer;    -   a razor blade, wherein the overcoat layer includes Chromium;    -   a razor blade, wherein the strengthening layer is the sole layer        of the strengthening coating;    -   a razor blade, wherein the thickness of the strengthening layer,        measured normal to the substrate side, is between 20 and 400        nanometres (nm), for example between 20 and 150 nm or between 40        and 250 nm;    -   a razor blade, further including a polymer coating over the        strengthening coating;    -   Aa razor blade, wherein the strengthening layer disorderly        includes areas having different proportions of titanium and        boron atoms; and

wherein, in at least one area, the proportion of boron and titanium iscomprised between y:1 and z:1, wherein y and z are comprised between 1.3and 1.99, and y is lower than z, and/or wherein, in at least one area,the proportion of boron and titanium is comprised between u:1 and v:1,wherein u and v are comprised between 2.01 and 2.3 and u is lower thanv.

According to another aspect, the present invention relates to a razorhead including a cartridge and a razor blade, the razor blade beingmounted in the cartridge.

According to another aspect, the present invention relates to a razorincluding a handle and a razor head wherein the razor head is beingattached to the handle.

In some specific embodiments, the coating is not a pure titaniumdiboride coating. It includes titanium and boron. One or more areas areboron-rich areas and/or one or more areas are titanium-rich areas. Yet,the dispersion of the titanium concentration within the layer can becontrolled in order not to exceed upper or lower thresholds, which wouldlead to loss of properties.

According to another aspect, the razor blade includes:

-   -   a razor blade substrate having a substrate edge portion in the        blade edge portion of the razor blade, the substrate edge        portion having a profiled geometry and having a tapering        geometry with two substrate sides converging toward a substrate        tip,    -   a strengthening coating deposited on the razor blade substrate        at least at the blade edge portion, the strengthening coating        covering the substrate tip, the strengthening coating having a        profiled geometry and having a tapering geometry with two        coating sides converging toward a coating tip,

wherein the strengthening coating includes a mixture of titanium andboron,

wherein the strengthening layer is deposited under conditions which,when applied to deposition on a flat witness sample, provide a coatingthe density of which is above 3.9 grams per cubic centimetre (g/cm³).

According to another aspect, the razor blade includes:

-   -   a razor blade substrate having a substrate edge portion in the        blade edge portion of the razor blade, the substrate edge        portion having a profiled geometry and having a tapering        geometry with two substrate sides converging toward a substrate        tip,    -   a strengthening coating deposited on the razor blade substrate        at least at the blade edge portion, the strengthening coating        covering the substrate tip, the strengthening coating having a        profiled geometry and having a tapering geometry with two        coating sides converging toward a coating tip,

wherein the strengthening coating includes a mixture of titanium andboron,

wherein a combined thickness of the blade substrate and strengtheningcoating, measured between the two coating sides orthogonal to a linebisecting the blade edge portion, at a distance of 5 micrometers fromthe coating tip, is between 1.8 and 2.5 micrometers, and preferablybetween 1.9 and 2.4 micrometers.

According to another aspect, a combined thickness of the blade substrateand strengthening coating, measured between the two coating sidesorthogonal to a line bisecting the blade edge portion, at a distance of20 micrometers from the coating tip, is between 5.1 and 7.3 micrometers,and preferably between 5.4 and 7.1 micrometers.

According to another aspect, the razor blade includes:

-   -   a razor blade substrate having a substrate edge portion in the        blade edge portion of the razor blade, the substrate edge        portion having a profiled geometry and having a tapering        geometry with two substrate sides converging toward a substrate        tip,    -   a strengthening coating deposited on the razor blade substrate        at least at the blade edge portion, the strengthening coating        covering the substrate tip, the strengthening coating having a        profiled geometry and having a tapering geometry with two        coating sides converging toward a coating tip,

wherein the strengthening coating includes a mixture of titanium andboron,

wherein a combined thickness of the blade substrate and strengtheningcoating, measured between the two coating sides orthogonal to a linebisecting the blade edge portion, at a distance of 20 micrometers fromthe coating tip, is between 5.1 and 7.3 micrometers, and preferablybetween 5.4 and 7.1 micrometers.

According to another aspect, a combined thickness of the blade substrateand strengthening coating, measured between the two coating sidesorthogonal to a line bisecting the blade edge portion, at a distance of5 micrometers from the coating tip, is between 1.8 and 2.5 micrometers,and preferably between 1.9 and 2.4 micrometers.

BRIEF DESCRIPTION OF THE DRAWINGS

Other characteristics and advantages of the present invention willreadily appear from the following description of some of itsembodiments, provided as non-limitative examples, and of theaccompanying drawings.

On the drawings:

FIG. 1 is a schematic drawing of a blade profile in sectional view,

FIG. 2 is a dark field transmission electronic microscope view of acoated sample,

FIG. 3 shows X-ray diffraction spectrums of the Ti and TiB_(x) layersdeposited under various conditions on a substrate,

FIG. 4 is a schematic drawing of a coated blade edge profile insectional view,

FIG. 5 is a schematic drawing of a coated blade edge profile insectional view,

FIG. 6 is a schematic drawing of a coated blade edge profile insectional view, and

FIG. 7 is a schematic view of a shaver,

FIG. 8 is a sectional view of a razor blade illustrating geometricalmeasurements,

FIG. 9 is a schematic top view of a deposition apparatus useful for themanufacturing of the blades,

FIG. 10 is a schematic side view of the apparatus of FIG. 9.

On the different Figures, the same reference signs designate like orsimilar elements.

DETAILED DESCRIPTION

Hereinafter, the present invention is described in detail with referenceto the accompanying drawings. Generally the razor blades comprise ablade substrate, which further includes a blade body and a blade edge.FIG. 1 shows a razor blade edge substrate 10 that includes tapered sides10 a, 10 b which meet in a blade tip 10 c. The shape of the blade edgesubstrate 10 can be angular or arched or the combination of these two.However, the special geometry and the material of the blade edgesubstrate 10 usually do not provide sufficient hardness for shavingpurposes and coating layers are implemented on the blade edge substrateto improve the hardness of the blade edge and thereby enhance thequality of the shaving. The coating layers enable to reduce the wear ofthe blade edge, improve the overall cutting properties and prolong theusability of the razor blade.

On FIG. 1, the blade edge substrate 10 is coated with a strengtheningcoating layer 16 and a lubricating layer 17. The lubricating layer,which may comprise fluoropolymer, is commonly used in the field of razorblades for reducing friction during shaving. The strengthening coatinglayer 16 is used for its mechanical properties. The strengtheningcoating layer 16 includes titanium and boron. More precisely, thestrengthening coating layer 16 is made of titanium and boron with a lowcontent of impurities. The content of impurities is kept as low aseconomically viably possible. The strengthening coating layer 16 can beprepared with various proportions of titanium and boron within thelayer. This means that there could be a mixture of titanium diboride(TiB₂) and/or other components including titanium and/or boron. Thecoating layer 16 includes Ti-rich and/or B-rich areas. “rich” is used inrelation to the normal stoichiometric respective concentrations of Tiand B compared to TiB₂. The material which constitutes the layer 16 canbe indicated as TiB_(x). For example, the coating layer 16 has localvariations of concentrations of these elements, having B-rich areas,where the atom ratio B:Ti is over 2, up to 2.3 (x included between 2.01and 2.3), and Ti rich areas, where the ratio B:Ti is below 2, down to1.3 (x included between 1.3 and 1.99). The local variations can berandomly arranged in the layer. These proportions of titanium, boron andtitanium diboride can provide additional improvements for the overallcoating of the blade edge substrate 10. So, in the present application,when it is referred to TiB_(x), it is referred to a coating as describedabove.

Referring to FIG. 2, a coating layer configuration is shown, wherein asubstrate S is covered by an interlayer 15 made of titanium which iscovered by a strengthening layer 16 made of TiB_(x). This layerconfiguration corresponds to a coating layer configuration on a razorblade edge.

The manufacturing of the coated blades can be made by sputter depositionfrom Ti and TiB₂ targets. As visible from FIGS. 9 and 10, the bladesubstrates S are loaded on bayonets 21 in the depositing chamber 22,which includes a Ti target 23, and two TiB₂ targets 24 a, 24 b. In someembodiments, the depositing chamber may also comprise a Cr target 25.For example, the four targets are provided as four corners of a square(seen from the top). For example, the two TiB₂ targets are facing eachother. Before the deposition, a sputter etching step can be carried out.The depositing chamber 22 is evacuated up to a base pressure of 10⁻⁵Torr using vacuum means 26. Then Ar gas is inserted from an Ar gassource 27 into the chamber 22 up to a pressure of 8 mTorr (8.10⁻³ Torr).By rotating the loaded bayonets connected together through a commonstructure 28 at a constant speed of 6 rpm using a motor 29, all targets,and notably the Ti and TiB₂ targets are operated under DC currentcontrol at 0.2 Amps. A DC voltage of 200-600 V is applied on thestainless steel blades for 4 minutes. During the sputter etching step,impurities are removed from the blade substrates and the targets throughbombardment of Argon ions.

For depositing the titanium interlayer 15, after the end of sputteretching step, the chamber pressure is adjusted to 3 mTorr. The Ti andTiB₂ target(s) are operated under DC current control at 3 and 0.2 Ampsrespectively while a DC voltage of 0-100 V is applied on the rotatingblades. The current on the TiB₂ targets (and the same on the Cr targetif present) is used to prevent elements from depositing on thesetargets. Adjusting the deposition time, a Ti layer of 10-100 nm, forexample of 10-50 nm is deposited on the edge of the blade samples.

For depositing the TiB_(x) strengthening layer 16, after the depositionof the Ti interlayer 15, the Cr, Ti and TiB₂ targets operatesimultaneously, with the current on the Cr target set to 0.2 Amps, thaton the Ti target(s) adjusted and the current on TiB₂ target(s) set to 3Amps. The current on the Cr target is used to prevent elements fromdepositing on that target. Further, the ratio of currents applied on theTi and TiB₂ targets is adjusted as a function of the desired compositionof the coating. A DC bias voltage of 0 to 600 V is applied on therotating blades. Adjusting the deposition time, a TiB_(x) layer of20-150 nm is deposited on the Ti layer. Alternately, a TiB_(x) layer of40-250 nm is deposited on the Ti layer. In general, a TiB_(x) layer of20-400 nm can be deposited on the Ti layer.

As more detailed in the following description a metal-containingovercoat layer 20 can be provided over the strengthening layer 16. Forinstance, on top of the TiB_(x) strengthening layer 16, a thin 10-50 nmCr layer 20 can be deposited, this layer configuration is depicted onFIG. 6. For this step, the coated blades can be moved to another sputtermachine, or it can be carried out in the same machine, including a Crtarget, as shown on FIGS. 9 and 10. The current on the Cr target(s) isset at 3 Amps and a bias voltage of 0-450 V is applied on the blades. Ifit is conducted in the same sputter machine, one may provide forprotecting the non-operating target(s) from contamination from theoperating target(s), and for preventing operation of non-operatingtargets at each step.

Referring to FIG. 2, the aforesaid coating layer configuration is shownwherein the substrate S is covered by a Ti interlayer 15. Further, theTi interlayer 15 is covered by a TiB_(x) strengthening layer 16.Moreover, layers 15 and 16 exhibit a nanocrystalline arrangement. In theTiB_(x) layer, the atoms of the nanocrystals are arranged in a hexagonallattice configuration. A layer exhibiting a nanocrystalline arrangementis also called a nanocrystalline layer. The nanocrystals can be definedas crystal structures having at least one, and notably all 3 maindimensions lower than 100 nanometres (nm). The Ti nanocrystals form thincolumns along the growth direction. The columns have diameters up to10-12 nm.

The Ti layer 15 is covered by a TiB_(x) strengthening layer 16 includingTiB₂ nanocrystalline areas wherein the atoms of the nanocrystals arearranged in a hexagonal lattice configuration. The TiB_(x) structuredoes not comprise any columnar structure, as visible on FIG. 2. Such afeatureless structure has interesting properties for a razor bladestrengthening coating.

The layer structure on substrate S, shown on FIG. 2, corresponds to alayer structure on a blade edge substrate 10. The growth conditions andthe applied bias voltage during formation of the TiB_(x) strengtheninglayer 16 provide a hard structure with preferable mechanical propertiesfor shaving, particularly compared to a TiB₂ columnar structure. Thepreferred growth conditions and the applied bias voltage on thesubstrate enable to grow the TiB_(x) strengthening layer 16 includingTiB₂ nanocrystalline areas wherein the atoms of the nanocrystals arearranged in a hexagonal lattice configuration.

On FIG. 3, an X-ray diffraction spectrum measurement is shown forsamples (T179-T185) covered by the aforesaid Ti interlayer 15 andTiB_(x) strengthening layer 16, where deposition of the TiB_(x) layerwere performed under different deposition conditions. The peaks P1 referto a TiB₂ (001) orientation in the TiB_(x) layer. Different depositionconditions result in different (001) peaks P1. That is, the depositionconditions result in different structure of the hexagonalnanocrystalline arrangement of the TiB_(x) layer. As depicted on FIG. 3,the peaks can vary in terms of intensity and broadening; however, theangular position of the peaks remains the same. The bias voltage,applied on the razor blade edge substrate 10, for achieving theaforesaid coatings is between 40V and 500V. The density of the TiB_(x)nanocrystalline strengthening layer 16 can not be measured on a razorblade edge. The same coating deposited on a flat sample has a densitywhich is between 3.9 g/cm³ and 4.4 g/cm³. An increased density isrelated to an increased strength of the layer.

As an example of thicknesses of the Ti interlayer 15 and the TiB_(x)strengthening layer 16, 40 nm of Ti interlayer 15 and 60 nm of TiB_(x)strengthening layer 16 can be considered. However, other dimensions ofthe thicknesses can be considered for both of the layers, wherein theoverall thickness of Ti interlayer 15 and the TiB_(x) strengtheninglayer 16 does not exceed 500 nm and, in some cases, does not exceed 150nm.

The razor blade, more particularly the razor blade edge substrate 10 iscovered by a strengthening coating 16 including a strengthening layer 16made of TiB_(x). In another embodiment, the strengthening coating 16might comprise a strengthening layer 16 and a Ti interlayer 15. Thestrengthening layer 16 disorderly includes areas having differentproportions of titanium and boron atoms, and in at least one area, theproportion of boron and titanium is included between y:1 and z:1,wherein y and z are included between 1.3 and 1.99, and y is lower thanz, and/or wherein, in at least one area, the proportion of boron andtitanium is included between u:1 and v:1, wherein u and v are includedbetween 2.01 and 2.3 and u is lower than v. The average proportion ofboron and titanium atoms in the strengthening layer 16 is between 1.3:1and 2.3:1. Overall titanium-rich coatings would, in average, have xincluded between 1.3 and 1.99. The razor edges of the razor blades mightbe coated by a strengthening coating including a sole strengtheninglayer 16, as described above. This coating layer configuration isdepicted on FIG. 4, where the blade edge substrate 10 is covered by astrengthening layer 16. The strengthening layer 16 is covered by apolymer coating (PTFE) 17. The razor blade substrate including the razorblade edge is made of stainless steel. A suitable stainless steelincludes mainly iron, and, in weight

-   -   0.62-0.75% of carbon,    -   12.7-13.7% of chromium,    -   0.45-0.75% of manganese,    -   0.20-0.50% of Silicon,    -   No more than traces of Molybdenum.

Other stainless steels can be used within the present invention.

The coating layer configuration of the blade edge substrate 10 mightinclude also an interlayer 15 between the razor blade edge substrate 10and the strengthening layer 16. This coating layer configuration isdepicted on FIG. 5, where the blade edge substrate 10 is covered by aninterlayer 15 which is covered by a strengthening layer 16. Theinterlayer 15 may be of titanium. The titanium interlayer 15 may be madeof columnar nanocrystals, without adversely affecting the strengtheninglayer 16. The strengthening layer 16 is covered by a polymer coating(PTFE) 17.

The thickness of the strengthening layer 16, measured normal to thesubstrate side, is between 20 and 150 nanometres (nm). Alternately, thisthickness is between 40 and 250 nanometres (nm). In general, this layercan be between 20 and 400 nm.

Furthermore, the strengthening coating might comprise a metal-containingovercoat layer 20 over the strengthening layer 16. For example, themetal-containing overcoat layer 20 is a layer of Chromium. This coatinglayer configuration is depicted on FIG. 6, where the blade edgesubstrate 10 is covered by an interlayer 15 which is covered by astrengthening layer 16. The strengthening layer 16 is covered by ametal-containing overcoat layer 20 which is covered by a polymer coating(PTFE) 17. The metal-containing overcoat layer can further improve theoverall hardness of the blade edge coating. And/Or, it can be used toassist adherence of the lubricating layer 17 on the strengtheningcoating.

This new blade coating can be used with razor blades with conventionalgeometry. However, it can also be used to coat razor blade substrateswith new geometry, while still exhibiting correct shaving performance.

A thickness t₅ of the blade (considering the substrate and thestrengthening coating, excluding the polymer coating), measured betweenthe two coating sides orthogonal to a line bisecting the blade edgeportion (see FIG. 8), at a distance of 5 micrometers from the coatingtip, can be for example between 1.8 micrometers and 2.5 micrometers, andpreferably between 1.9 and 2.4 micrometers, when measured using confocalmicroscopy.

A thickness t₂₀ of the blade (considering the substrate and thestrengthening coating, excluding the polymer coating), measured betweenthe two coating sides orthogonal to a line bisecting the blade edgeportion (see FIG. 8), at a distance of 20 micrometers from the coatingtip, can be for example between 5.1 micrometers and 7.3 micrometers, andpreferably between 5.4 and 7.1 micrometers.

Furthermore, FIG. 7 illustrates two above described razor blades whichare mounted into a razor cartridge 105 to form a razor head 110 that isconnected to a razor handle 201 to form a shaver 200 for shavingpurposes.

The razor blades with the above described strengthening coatings werealso tested. A first test includes hardness measurements performed oncoatings deposited on flat samples. Deposition of the TiB_(x) coating,as defined above, on flat samples, revealed that the hardness of thenanocrystalline strengthening layer 16 reached up to 15.8 GPa, which ismuch more than the hardness obtained for standard current coatingsdeposited on the same flat samples. Greater hardness of the coating onrazor blades can therefore be expected.

The aforementioned coated razor blades were also compared with standardproduction blades. The blades coated by Titanium, TiB_(x), Chromium andPTFE layers, as described above, were compared to standard productionblades coated by Chromium, CrC and PTFE layers. The substrate's materialand profile, the total inorganic coating thickness and the thickness ofthe PTFE coating was the same for the blades according to the presentinvention and for the standard production blades. The specific testinvolves repeating cutting action of the blade on a moving felt, using aload cell for measuring the load on the blade for a series of 10 cuts.The test resulted in load ranges for the last (10th) cut that were atleast 39% lower than the load of blades from standard production. Thisresult (see Table 1) shows that the blades with the above describedTiB_(x)-containing coating preserve their cutting ability, shape andintegrity, in a more effective manner during cutting action.

The damage imposed on the blade edge after 10 cuts during theabove-described test was also evaluated with an optical microscope. Thedamage on the blade edge tip was quantified in terms of area of missingmaterial (i.e. material that has been broken and removed from the edge)and area of intense deformation. TiB_(x) coated blades resulted in a 90%decrease of the missing and/or intensely deformed material area ascompared with blades from standard production. This result (see Table 1)shows the increased durability of the blades with the aforesaid TiB_(x)coating. The increased durability could allow employing thinner bladeedge profiles in razor blade products that would in turn be beneficialin the shaving performance of the product in terms of fluidity andoverall evaluation.

TABLE 1 Cutting force results and edge damages for TiB_(x) andconventional coatings Force at 10_(th) cut Area of damages Razor bladesample (kg) (μm²) Conventional coating 3.19 51822 TiB_(x) 1.95 6169

Above, an embodiment was presented wherein an overall Ti-rich TiB_(x)layer can be deposited by adjusting the current ratio of the Ti and TiB₂targets during simultaneous operation of those targets. However, thereappears to be other ways to obtain the above-described coating based onsuitable choices of operating parameters such as current applied on thetargets, blade bias voltage, displacement speed of the blades, chamberinner pressure. In particular, due to different deposition yields ofTitanium and Boron from the TiB₂ targets, boron-rich areas can beobtained. The average proportion of boron and titanium atoms in thestrengthening layer 16 is between 2.01:1 and 2.3:1.

Outside from the scope of the original claim 1, these parameters couldbe adjusted in order to deposit a TiB₂ coating. Although the TiB₂coating would not exhibit the composition of the original claim 1 whichmakes the coating particularly suitable as a razor blade coating such asexemplified above, it is contemplated that some TiB₂ coatings could beachieved that could also show some benefits as a razor bladestrengthening coating. Some preliminary tests suggest that a razor bladewith a specific profile as disclosed above could benefit from titanium-and boron-containing coatings for increased shaving performance. Somepreliminary tests also suggest that a razor blade with a dense titanium-and boron-containing coating as discussed above could provide increasedshaving performance.

Thickness data for the layers of the strengthening coating can beobtained by Auger Electron Spectroscopy Depth Profiling (AESDP). Themeasurement can be performed on the razor blade itself (for exampleafter getting rid of the polymer coating, or before applying the polymercoating).

Auger Electron Spectroscopy Depth Profiling is accomplished by excitinga blade edge surface with a finely focused electron beam, which causesAuger electrons to be emitted from the surface of the blade edge. Theseelectrons relate to the material located approximately up to 5 nm deepfrom the surface. They are detected by use of an electron spectrometerconsisting of an energy analyzer and an electron detector system. Themeasured energies of the Auger electrons can be correlated tocorresponding elements of the analyzed material.

To record elemental depth profiles of selected elements, the samplesurface is removed, for example sputtered away by bombardment with Ar+ions. The removal rate (in nanometres/minute) of the sputtering processon this kind of coating is known from previous calibration measurements.

The profiling experiment is stopped when the Auger Electron Spectroscopydetermines that the main material is the substrate material (most oftenstainless steel in the field of razor blades). Thus, knowing the overallthickness of the coating, it is possible to determine at which deptheach of the measurements was performed.

The analyzed region for the survey spectra and depth profile can belocated very close to the tip of the blade (5-10 μm away from the edgetip). Its size is of the order of magnitude 10 μm (for example a squarepatch of 10 μm×10 μm).

Prior to AES analysis, the blade samples are mounted on a sample holderand introduced into the ultrahigh vacuum chamber of the Auger ElectronSpectrometer. Auger survey spectra are measured on the as receivedsurface and after certain sputter times depending on profilingintensities, looking for the elements located in the thin film on theblade edge.

Depth profiling can be carried out by sputtering, for example byapplying 3 keV Ar+ ion energy. Accurate depth scale quantification ispossible by applying pre-calibrated sputter rates (i.e. materialthickness removal as a function of time). These sputter rates aredetermined on reference standards with the same coatings as the analyzedsamples. These samples were prepared by depositing on flat substratesthin films of identical composition, and deposited under the sameconditions, as the layers on the blade edge and measuring theirthickness by another profiling method in order to calibrate the AESmethod.

The other profiling method could be for example to place a mask on asample to be coated and, further to deposition, to remove coatingmaterial where the mask was placed, so as to measure the height of thestep between the remaining coated material and the substrate where thecoating material was removed.

Alternatively, an approximated value for sputter rates can be determinedfrom known sputter rates applied to the coating deposited on thecertified reference material BCR-261T (Ta₂O₅(100 nm)/Ta-sheet).

Hence, according to one aspect, one applies a method for determining arazor blade strengthening coating composition, wherein one repeatedlyperforms:

-   -   One measures the surfacic composition of the coating and,    -   One removes material from the coating at a given sputter removal        rate,

until one reaches an underlying layer or the razor blade substrate and

using sputter removal rate calibration data for the coating and thetotal strengthening coating thickness from another measurement method,one attributes the measured surfacic compositions to a depth within thecoating. This determination method can be applied for a TiB_(x) coating,but could be applied to other strengthening coatings as well.

1. A razor blade comprising: a blade substrate having a substrate edgeportion, the substrate edge portion having a tapering geometry with twosides converging toward a substrate tip; and a strengthening coatingdeposited on at least the blade substrate edge portion, covering the twosides of the substrate tip, the strengthening coating including ananocrystalline layer made of a mixture of titanium and boron, whereinthe nanocrystalline layer includes areas of non-columnar titaniumdiboride.
 2. The razor blade according to claim 1, wherein the averageproportion of boron and titanium atoms in the strengthening layer isbetween about 1.3:1 and about 2.3:1.
 3. The razor blade according toclaim 1, wherein the strengthening layer disorderly includes areashaving different proportions of titanium and boron atoms.
 4. The razorblade according to claim 1, wherein the strengthening layer is depositedunder conditions which, when applied to deposition on a flat witnesssample, provide a coating having a density of between about 3.9 gramsper cubic centimeter (g/cm3) and about 4.4 grams per cubic centimeter(g/cm3).
 5. The razor blade according to claim 1, wherein thestrengthening coating includes an interlayer between the blade substrateand the strengthening layer.
 6. The razor blade according to claim 5,wherein the interlayer comprises titanium.
 7. The razor blade accordingto claim 5, wherein the interlayer includes titanium nanocrystals havingcolumns with diameters of up to 10-12 nm.
 8. The razor blade accordingto claim 1, further comprising a metal-containing overcoat layerdeposited over at least a portion of the strengthening coating.
 9. Arazor blade comprising: a blade substrate having a substrate edgeportion, the substrate edge portion having a tapering geometry with twosides converging toward a substrate tip; and a strengthening coatingdeposited on at least the blade substrate edge portion, covering the twosides of the substrate tip, the strengthening coating including ananocrystalline layer made of a mixture of titanium and boron, whereinthe nanocrystalline layer includes featureless crystallites.
 10. Therazor blade according to claim 9, wherein the featureless crystalliteshave a dimension between 2 and 15 nanometers.
 11. The razor bladeaccording to claim 9, further comprising a metal-containing overcoatlayer deposited over at least a portion of the strengthening coating.12. The razor blade according to claim 11, wherein the overcoat layercomprises chromium.
 13. The razor blade according to claim 9, whereinthe strengthening coating includes an interlayer between the bladesubstrate and the strengthening layer.
 14. The razor blade according toclaim 13, wherein the interlayer includes titanium nanocrystals havingcolumns with diameters of up to 10-12 nm.
 15. The razor blade accordingto claim 13, wherein a combined thickness of the strengthening layer andthe interlayer does not exceed about 500 nanometers (nm).
 16. The razorblade according to claim 9, wherein a combined thickness of the bladesubstrate and the strengthening coating, measured between the twocoating sides orthogonal to a line bisecting the blade edge portion, ata distance of about 5 micrometers from the coating trip, is betweenabout 1.8 and about 2.5 micrometers.
 17. The razor blade according theclaim 9, wherein a combined thickness of the blade substrate and thestrengthening coating, measured between the two coating sides orthogonalto a line bisecting the blade edge portion, at a distance of about 20micrometers from the coating tip, is between about 5.1 and about 7.3micrometers.
 18. A razor blade comprising: a blade substrate having asubstrate edge portion, the substrate edge portion having a taperinggeometry with two sides converging toward a substrate tip; astrengthening coating deposited on at least the blade substrate edgeportion, covering the two sides of the substrate tip, the strengtheningcoating including a nanocrystalline layer made of a mixture of titaniumand boron; and a metal-containing overcoat layer deposited over at leasta portion of the strengthening coating, the overcoat layer comprisingchromium.
 19. The razor blade according to claim 18, wherein thestrengthening coating includes an interlayer between the blade substrateand the strengthening layer.
 20. The razor blade according to claim 19,wherein the interlayer includes titanium nanocrystals having columnswith diameters of up to 10-12 nm.